9 . Application to Proton Therapy

9.1 Background to Proton Therapy The use of proton beams for radiation treatment was proposed by Robert R. Wilson in 1946 [286]. Wilson referred to the ballistical aspects of the proton beam dose distribution as a rationale for the new modality. Heavy charged particles such as protons produce an energy deposition profile in tissue which is superior to profiles attainable using photon or electron irradiation. The dose distribution for a monoenergetic proton beam features a low entrance dose region followed by a slowly rising dose until the proton Bragg peak is reached, near the end of the range, where the dose rises rapidly. The beam energy is generally spread to modulate the proton range and provide a uniform high dose over the target tissue. This profile also features a moderate entrance dose and almost zero dose beyond the target [99].